Apparatus for treating metal articles



April 1 8, 1939. D. c. TURNBULL APPARATUS FOR TREATING METAL ARTICLES Filed July 14, 1936 6 Sheets-Shea?l l mvEN-roR DAvm CEJRNBULL.

. MM; ATTORNEY a. l WW M April 18, 1939,. p. c. TURNBULL APPARATUS FOR TREATING METAL AARTICLES Filed July 14, 1936 6 Sheets-Sheet 2 L I.- w R ON Tm WT WC m m D lrlAlllllIl ATTORNEY April 18, 1939. D. c. TURNBULL APPARATUS FO'R TREATING METAL ARTICLES Filed July 14, 1936 6 Sheets-Sheet 3 INVENTO'R DAvlD C. TuRNBuLL.

M am ATTORNEY 6 Sheets-Sheet 4 ATTORNEY lNvENToR .DAvm C. TuRNsuLL.

April 18, 1939. D. c. TURNBULL APPARATUS FOR TREATING METAL RTICLES Filed July 14, 1956 O O o o a, 0, s O o im PHHIIMHHHHHIIHH B N April 18, 1939- D. c. TURNBULL 2,154,879

APPARATUS FOR TREATING METAL ARTICLES Filed July 14, 1936 6 Sheets-Sheet 5 INVENTOR DAvm C. Tumvsuu..

BY @MAJ NOW/Lg ATTORNEY April 18, 1939- D. c. TURNBULL 2,154,879

APPARATUS `FOR TREATING METAL ARTICLES Fled July 14, 1936 6 Sheets-Sheet 6 Q95 f5 72 7:5/ 74 7U/ `75 .az 64 52 7]/ 6 6 DAvm C.TuRNuLL.

Lj/?. BY

lg www ATTORNEY Patented Apr. is, 1939 UNITED STATES APPARATUS FOR TREA'I'ING METAL ARTICLES David G. Turnbull, Mishawaka, Ind., assignor to American Foundry Equipment Company,

Mishawaka, Ind., a corporation of Delaware Application July 14, 1936, Serial No. 90,476

21 Claims.

This invention relates to apparatus for treating metal articles.

In cleaning, polishing, hardening, or otherwise treating the surfaces ofmetallic objects, theobjects treated should be manipulated insuch manner that all or predetermined portions of theA various types of tumbling apparatus now in use.'

However, 'where thearticles are large and heavy, l5; or irregular in shape, or fragile and breakable, tumbling is n'ot suitable. Further, where the articles'have cavities or projections, it is necessary to present these cavities or projections to the abrasive stream in such a manner that all areas will be uniformly treated. To attain maximum efficiency and economy the apparatus should be so designed that the process can be carried out continuously without shutting down the apparatus, as is necessary in batch operations.

According to the present invention, each article to be treated is supported on a carriage, and the carriage is urged along a predetermined path to carry the article through the treating stream. The article is rotated or turned on the carriage simultaneously with its movement through the stream, thereby uniformly exposing the various surfaces of the article to the effect of the stream.

The apparatus for carrying out the process includes one or more abrasive projectors, preierably of the centrifugal throwing wheel type having means associated therewith for controlling the direction of flight of the treating par- 40 ticles. The article-supporting carriages move through the stream on a suitable track. Means are provided for advancing the carriage or carriages at the proper rate of speed. The driving means may include a exible endless member supported for traveling movement and having driving engagement with the carriage or carriages. Each carriage may be provided with spaced pairs of rotatably mounted supporting elements adapted to engage the article. A driving member may be disposed adjacent the path of movement of the carriage in a position to engage and rotate the supporting elements, thereby to turn the article on the carriage, while the latter is advanced throughA the stream of treating material.

'no attention on the part of the operator.

The apparatus herein described is suitable for treating numerous types of articles, such as irregular, heavy or fragile castings, forgings and other machine and structural members. For exy ample, the apparatus is well adapted for handling andtreating cranki shafts and ksimilar irregularly shaped articles. The articles are positively advanced through the treating stream under controlled speed and are rotated in the stream under controlled spedand thus may be exposed for treatment for any desired period. The apparatus may be operated continuously and substantially automatically and requires little or If desired, suitable automatic apparatus may be provided for delivering the articles to the apparatus and conveying the treated articles therefrom. t

An object of this invention is to provide an improved apparatus for cleaning, polishing, hardening or otherwise treating metallic objects.

Another object ,of this invention is to provide an improved apparatus for cleaning and treating metallic articles which are large and heavy, or irregular in shape, or fragile and breakable, or articles of such a character that their surfaces cannot be effectively exposed for treatment by tumbling action.

Another object of this invention is to provide an improved apparatus for simultaneously advancing and rotating articles to be cleaned through an abrasive stream so as to uniformly expose the surfaces thereof to abrasive treatment.

Another object of this invention is to provide an improved apparatus for continuously treating metal articles which is relatively simple in construction, requires little or no attention on the part of the operator, which is strong and durable, and is admirably adapted for continuous production operations.

Various other features and advantages of the invention will be apparent from the following particular description and from an inspection of the accompanying drawings. y

Although the novel features which are believed to be characteristic of this invention will be particularly pointed out in the claims appended hereto, the invention itself, as to its objects and advantages, and the manner in which it may be carried out, may be better understood by referring to the following description taken in connection with the accompanying drawings forming a`. part thereof, in which:

Fig. 1 is a somewhat diagrammatic side elevational view of one form of apparatus suitable for carrying out the-invention, certain parts of the structure being broken away to expose the interior;

Fig. 2 is a top plan view-of the apparatus shown in Fig. 1;

Fig. 3 is an enlarged fragmentary cross-sectional view of the apparatus, taken along line 3-3 of Fig. 2;

Fig. 4 is an enlarged fragmentary cross-sectional view of the apparatus, taken along line 4-4 of Fig. 2;

Fig. 5 is an enlarged transverse cross-sectional view of the apparatus,- taken along line 5-5 of Fig. 1;

Fig. 6 is an enlarged top plan view of one of the article-supporting carriages together with a portion of the associated driving element;

Fig. 7 is a side elevational view of the carriage shown in Fig. 6, and

Fig. 8 is a somewhat diagrammatic sectional detail of the centrifugal abrasive projector.

In the following description and in the claims, various details will be identified by specific names for convenience, but they are intended to be as generic in their application as the art will permit. Like reference characters denote like parts in the several figures of the drawings.

In the drawings accompanying and forming part of this specification, certain specific disclosure of the invention is made for purposes of eX- planation, but it will be understood that the details may be modified in various respects without departure from the broad aspect of the invention.

'I'here is shown in Figs. 1 to 5 inclusive, by Way of illustration, apparatus constructed in accordance with the invention. The apparatus includes a housing I having a treating chamber 2, a loading chamber 3 having a loading opening 4, and an unloading chamber 5 having an unloading opening 6. Extending throughout the chamber is a conveyor 1 adapted to carry the articles to be treated from the loading chamber 3 through the treating chamber 2 to the unloading chamber 5, which conveyor is more fully described hereinafter.

One or more abrasive projectors may be suit- `ably mounted on the top wall of the housing I for projecting a corresponding number of streams of treating material into the chamber. In the present example two such projectors A and B are shown, which project the abrasive streams designated a and b, respectively. Although the projectors A and B may take various forms, preferably they are of the centrifugal throwing wheel type having means associated therewith for controlling the direction of flight of the thrown treating material.

The wheel I includes a plurality of throwing blades I4 which extend in a generally radial direction from adjacent the periphery of the wheel to points inwardly short of the -center to provide a central space I5. Disposed in the space I is an impeller I6 having a plurality of radi-l ally directed vanes I1. Surrounding and spaced from the impeller I6 is a relatively stationary independently mounted control member I8 having a discharge outlet I 9.

The blades I4 may be supported by one or more side Wall members I2 and I3 which are mounted on a shaft 20 rotatable in a bearing 2I. The impeller I6 preferably rotates with the blades and may be connected to the drive shaft 20. A motor 22 mounted on a base 23 is connected to the shaft and projected abrasive stream relative to the con-- veyor 1. The projector B may be constructed and ,mounted similarly to projector A, but preferably rotates in the opposite direction for a purpose which will hereinafter appear.

Each wheel may be supplied with treating material from a hopper 30 through a conduit 3l extending to feed-pipe 32 which conducts the material to the impeller I1.

The treating material, sometimes referred to as abrasive, may comprise granular material, such as cracked steel grit, steel shot, sharp quartz sand, or other cleaning, abrading, polishing or hardening material. The material selected will, of course, depend upon the surface effect desired. It will therefore be understood that where the term "treating material or abrasive is used it includes within its range all materials useful for cleaning, polishing, hardening or otherwise modifying the surface of metallic objects.

When the wheel I0 is rotated and supplied with abrasive, the impeller I6 throws the abrasive through the control cage opening I3 and into the path of the rotating throwing blades I4. 'I'he abrasive is carried along the leading faces of the blades I4 and is projected therefrom adjacent the periphery of the wheel at the desired treating velocity. The abrasive spreads out from the wheel in a fan-shaped stream a which produces an impingement pattern in the shape of an elongated strip. The direction of' flight of the treating material .is controlled by the clock dial position of the outlet I3 of the control member I 8.

It will be noted that each abrasive stream a and b extends throughout a considerable range of angularity which may approach 90. Preferably, the streams are directed in reversed directions so that the range of angularity of the combined streams approaches 180?.

'I'he abrasive whichis thrown by the projectors A and B against the work finally falls onto the floor 34 and'is transported to a collecting trough 35. A screw conveyor 36 is disposed in the trough 35 and is driven by a suitable source of power (not shown) to convey the projected abrasive to an elevator 31. The elevator may include an endless flexible belt 38 trained over drums 39 and 40 and carrying buckets 4I. A motor 42 connected by a drive 43 is provided for actuating the belt 38 and causes the buckets 4I to elevate the abrasive from the trough 35 to a conduit 45 from which the abrasive flows by gravity to the hopper 30.

Referring now to Figs. 6 and 7, there is shown one form of carriage 50 constituting a component partl of the conveyor 1. The carriage 50 supports the articles to be treated and conveys them through the streams of abrasive a and b. Preferably, a plurality of carriages 50 are provided which pass through the abrasive streams in close succession.

Each carriage 50 may include end rails 5I and 53 and side rails 52, secured together to form a generally rectangular frame. Suitable bracing rails 54 may be connected to the end rails 5I cross-rail l.

and 59. Extending transversely across one end of the frame is a cross-rail 55 adapted to rotatably carry'a pair of supporting heads or rollers heads cooperate to turn the articles supported thereon when rotated.

Extending transversely across the other end of the carriage 50 is a cross-rail 59 mounting a second pair of supporting heads or rollers 60 also providing a supporting periphery, which preferably is in alignment with the supporting peripheries provided bythe heads 56. I'he cross-rails 59 may be secured to a pair of brackets 6i slidably supported on the side rails 52 and adapted to be adjustably secured by bolts 62 or other members extending through openings 63 and 64 in the brackets 6| and side rails 52. respectively. It will thus be noted that the supporting heads 60 may be spaced from the supporting heads 56 any desired distance to best accommodate the articles to be treated.

The front end of the carriage 50 is connected to and supported by a pair o f spaced parallel driving chains 10, each of which includes links 13 and 14, secured together by pins 68 carrying rollers 15. A shaft 1|l is secured to the carriage 50 and extends laterally therefrom to engage the chains 10. Each end oi the shaft 1| has a reduced portion 12 extending through links 13 and 1 4 and rollers 15. 'Secured to and extending across the frontend of the carriage 50 is a rearwardly directed plough or scooper 61, the function of which will hereinafter appear.

The rear end of the carriage 50 is supported on wheels 65 rotatably mounted on stud shafts 66, suitably secured to the rear ends of the side rails52.

Each driving chain 10 may be trained over a pair of driving sprockets 16 located in the loading chamber 3 ,and unloading chamber 5, respectively, and rotatably carried on shafts 11 journalled in bearings 18. The driving sprockets 16 in the unloading chamber 5 may be driven by a motor 19 connected by a drive 80 and a speed reducer 8| to a shaft 82. A drive 88 and sprocket 84 may operatively connect the shaft 11 to the shaft 92.

Each chain 10 is supported by and adapted to ride along an upper chain track 86 supported on brackets 81 extending from the wall of the housing I and a lower chain track 88 supported on brackets 89.

The wheels 65 of the several carriages 50 are supported and guided by upper carriage tracks 90, 90 mounted on the brackets 81, 81, between and below the chain tracks 86. The wheels 65 are preferably of such diameter that each carriage is substantially horizontaiwhen supported on the chains 10 and the carriage tracks 90, 90.

The left-hand ends 9| of the tracks 90, 90 (as viewed in Fig. 3) are curved downwardly and are supported by brackets 92, 92. Return tracks 93, 93 are mounted on brackets 94, 94, adjacent the track ends 9|, 9|, and lower carriage tracks 95, 95 mounted on brackets 89, 89 extend from the return tracks 93, 93 toward the other end of the housing Each lower carriage track 95 has an inclined portion 96 which extends to a spur 91 supported on a bracket 98 approximately at the height of the upper carriage track 90.

Adjacent each spur 91 is a switch 99, swingable about a pivot |00 carried on brackets |0|, and

adjacent the end of each upper track 06 is a secbridge |02 mounted on brackets |05 may extend between each set of switches 99 and-|03.

Disposed adjacent and extending along the path of movement of the carriages 50 on each side thereof is a drivingroll ||0 carried on a shaft extending through openings H2 in the housing and journalled in bearings H9. A motor ||5 may be connected through a speed reducer ||6 and drives i |1 tothe shafts for rotating the driving rolls ||0.

'I'he operation of the apparatus is as follows: 'I'he wheels I0 and are energized by their driving motors 22, 22 and abrasive is supplied to the wheels from the hopper 30.y .The wheels |0 and throw fan-shaped streams of abrasive a and b into the treating chamber 2.

The motor 19 is energized and actuates the driving sprockets 16 in the unloading chamber to cause each of the chains 10 to travel around an endless path determined by the sprockets -16 Vand the upper and lower chain tracks 96 and 88; the

rollers 15 of the chains 10 ride along on the moves into the treating chamber 2 toward the position Ie and enters the abrasive stream a. The

treating particles strike the crank shaft c at angles which vary continuously as the crank shaft passes through the stream thus impinging against all of the vertical surfaces as well as the horizontal surfaces. During movement of the carriage 50 through the treating chamber 2, the supporting heads 56 and 60 bear against the corresponding driving rolls ||0, ||0, which causes the supporting heads 56 and 60 to rotate about their axes. This causes the crank shaft c to rotate about its axis and thus expose all of the surface portions to the stream. In the course of its travel through the streams a and b all surfaces are fully and uniformly treated.

When the carriage 50 reaches a position, such as the position f, the crank shaft c may be re- `moved and the front end of the carriage 50 is carried around a loop defined by the/chains 10 passing around the sprockets 16 at the unloading end of the apparatus. The rear end of the carriage, however, is guided downwardly by the track ends 9| and caused to reverse its direction by the return reversing tracks 93. The carriage 50 is then moved in the return direction along the lower tracks 88, 88 and 95, 95, with its rear end preceding the forward end.

When the carriage 50 approaches the loading end of the apparatus the wheels 65 ride up the inclined tracks 96 and onto the spurs 91, the wheels 65 lifting the switches 99, 99. The forward end of the carriage is carried around the sprockets 16, and as the forward end of the Acarriage 50 begins to move to the left the rear end rides over the lowered switches 99, 99.

`As the forward end of the carriage 50 is raised,

it raises the switches |03, |03 and passes up through the switches and is moved forwardly and onto the upper chain tracks 80, 86, the wheels 65 riding over the bridges |02, |02 and over the closed switches |03, |03. The carriage 50 is then again in the position d ready to receive another crank shaft c. A

During the movement of each carriage 50 along the lower tracks 88, 88 and 95, 95, the scraper 6l carriesthe spent abrasive along the floor 34 and causes it to drop into the trough from whence it is returned to the hopper 30, as above described.

Various modifications may be made in the structure to adapt it for various uses. Any suit,- able number of carriages may be employed and the supporting heads may be replaced by other types of supporting elements, depending upon the articles which are to be treated.

, Where the articles to be treated are narrower than` the impingement pattern of the streams a and b, the positions of thewheels l0 and Il may be adjusted so that their impingement patterns extend in the direction of movement of the articles through the apparatus, thus effecting a maximum speed of operation. Where the arti' cles are relatively wide, the wheels are adjusted angularly on the housing so thattheir impingement patterns extend jover a greater distance laterally with respect to the path of movement of the articles, thus insuring that all portions of the articles pass through the streams.

From the foregoing it will be seen that the present invention provides apparatus for eiectively treating large and heavy, or awkwardly shaped, brittle or fragile castings, forgings, and other metal articles. 'Ihe supporting heads provide an especially suitable arrangement for rotating the articles such as crank shafts and the like during treatment. The carriages are positively driven and guided and the articles may be rotated at any desired speed to most effectively expose the desired surface areas to abrasive treatment.

It will benoted that during the entire cycle of movement of each carriage, the carriage is not inverted but is maintained in upright position. Thus it is possible, if desired, to allow the article to remain on the carriage and pass itthrough the stream a plurality of times without removing it from the carriage.

While certain novel features of the invention have been disclosed and are pointed out in the annexed claims, it will be understood that various omissions, substitutions and changes may be made by those skilled in the art without departing from the spirit of the invention.

What is claimed is:

1. In an abrading machine, a centrifugal abrasive propelling mechanism operative to project a fan-shaped stream of abrasive particles having an elongated impingement pattern, a pair of spaced endless supporting belts, drive mechanism for advancing the upper ight of said supporting belts in the general direction of the longitudinal axis of said impingement pattern, a frame exs tending between and connected to said supporting belts, a pair of rollers mounted on said frame having their peripheries positioned in adjacent relationship to provide opposed and divergent supporting surfaces for the workpiece, and driven means operative to rotate said supporting rollers to rotate the workpiece during its linear advance through said stream.

2. Apparatus for blast cleaning metallic articles including in combination, an abrasive throwing wheel operative to project a controlled stream of abrasive at blasting velocities so as to dene an elongated impingement pattern, a movable support, a continuous flexible member for advancing said movable support in the general direction of the longitudinal axis of said impingement pattern, spaced rotatable elements mounted on said support for supporting the articles to be cleaned, and driven means positioned outside the path of said abrasive stream and mounted independently of said movable Isupport but adapted to attachably and detachably engage said rotatable elements to rotate said elements and the articles supported thereon during passage of the articles through said stream.

3. Apparatus for blast cleaning and treating metal articles including, a track comprising spaced track members, a centrifugal abrasive propelling mechanism operative to project a ianshaped stream of abrasive particles between said track members, an article-supporting carriage spanning said track members and movable along said track, a driven member attached to said *carriage` for advancing said carriage' along ysaid track, rotatable means mounted on said carriage on'which the article is adapted to rest, and a driven element mounted, independ# ently of said carriage and normally beyond the reach of said abrasive stream, said rotatable article-supporting means being movable'into operative engagement with' said driven element prior to movement of the carriage-supported article into the abrasive blast whereby to rotate the article in said stream as the carriage is linearly advanced through said stream, said article rotatable means moving outv of engagement with said driven element when the article has completed lits passage through the abrasive stream. 1

4. Apparatus for blast lcleaning and treating metal articles including, a centrifugal abrasive propelling mechanism operative to project a stream of abrasive particles, spaced conveyors for moving articles to be treated through said stream, a support extending between and connected to said spaced conveyors, spaced supporting rollers rotatably mountedl on said support, said rollers having their peripheries positioned tolcon'stituteopposed anddivergent supporting surfaces for said articles, and a member driven independently of said conveyors adapted to frictionally engage the periphery of one or more of said rollers and rotate the varticle supported on said rollers during its linear travel throughsaid stream.

`5. Apparatus for treating metal articles' including, means for projecting a stream offabra sive particles, anv article-supporting carriage, a pair of spaced endless driving means. supporting one end of the carriage, a pair of spaced tracks supportingthe opposite end lofthe carriage, and means for actuating saidendless driving means to advance the article supported on said carriage through said stream. v

6. Apparatus for treating metal articles including, means for projecting a stream of abrasive material, a pair of spaced endless conveyors for moving articles to be' treated through 'said stream, a member extending between and-connected to said spaced conveyors, spaced sup porting rollers rotatably mounted on said mem' ber, said rollers having their peripheries adjacent and adapted to constitute opposed and divergent supporting surfaces for said articles, and driven means mounted independently of said conveyors and positioned outside the path o! said abrasive stream for rotating said rollers.

-7. Apparatus for blast cleaning metallic arti-y cies including in combination, a centrifugal projector operative to throw a directed stream of abrasive at blasting velocities, an article-supporting carriage, spaced tracks for supporting said carriage for linear movement therealong, means for' advancing said article-supporting carriage through said stream, means for supplying abrasive particles to said projector, a hopper for receiving abrasive, and a scraper associated with said carriage lfor transporting the abrasive thrown by said projector to said hopper'.

8. Apparatus for treating metal articles, including means for projecting a stream of abrasive material, a series of carriages adapted to support articles to be treated, an endless driving element, means permanently connecting'said carriages to said driving element, means for supporting said carriages for linear movement, and means for guiding said carriages through said stream, said last means including a forward track, a return track, a reversing track and a switch connecting said forward and return tracks to provide a continuous, endless guiding means for said carriages.

9. Apparatus for treating metal articles, including centrifugal means for projecting a stream of abrasive material, means including a carriage having a rotatable element for supporting an article to be treated, meansfor advancing said carriage to carry said article through said stream, a rotatable member extending along the path of said rotatable element and engageable therewith for driving said rotatable element during at least a lportion of its travel, and means' for moving said carriage in a reverse direction out of the effective range4 of said stream.

10. Apparatus for treating metal articles including centrifugal means for projecting a fanshaped stream of abrasive material having an elongated impingement pattern, means including a plurality of freely rotatable supporting rollers for supporting an article to be treated, means for advancing said supporting rollers in a continuous, endless path to carry said article through said stream, an elongated driving roll extending along the path of said rollers, and meansA mounting said driving roll for driving engagement with at least one of said supporting rollers for rotating it during at least a portion of the travel thereof through said stream.

11. In an abrading machine, centrifugal abrasive propelling mechanism operative to project a fan-shaped stream of abrasive particles having an elongated impingement pattern, a pair.

of spaced endless supporting members between which said fan-shaped stream is projected, means for advancing the upper night of said supporting members in the general direction of the longitudinal axis of said impingement pattern, a frame member extending between and connected to said supporting members, a workpiece-supporting means rotatably mounted on said frame member, and driven means positioned to one side of said workpiece-supporting means operative to rotate said workpiece-supporting means and the workpiece supported thereon during the passage of said workpiece through said abrasive stream.

12. In an abrading machine, a centrifugal abrasive propelling mechanism for projecting a stream of abrasive particles, rotatable supports, a pair of spaced flexible supporting members trained over said rotatable man. driving mechanism for advancing said flexible members,

a frame extending between and connected to said flexible members, article-supporting means rotatably mounted on said frame, and drive" means independent of said frame for rotating said article-supporting means tol rotate the article during its linear advance through said stream.

13. In an abrading machine, a pair of spaced iiexible supporting chains, a pair 'of rotatably 10 mounted sprockets supporting each of said chains, a centrifugal abrasive propelling mechanism positioned to project a stream oi' abrasive particles between said spaced chains, drive means for ad- `vancing a night of said chains linearly and in c `and drive means for rotating said drive roll to rotate the workpiece during its linear advance through said stream. 1

14. In an abrading machine, a centrifugal ,abrasive projecting mechanism operative to project a fan-shaped stream of abrasive particles having a generally elongated impingement pattern, a -workpiece-supporting carriage, spaced generally parallel extending elements supporting said carriage, means for advancing said carriage through said stream in the general direction of the longitudinal axis of said impingement pattern, paired sets of workpiece-supporting rollers rotatably mounted on said carriage, a pair of spaced drive rolls between which said fan-shaped stream is projected, means for rotating said drive rolls, said workpiece-supporting rollers being positioned to be moved into operative engagement with said drive rolls whereby to rotate said supporting rollers and the workpiece supported thereon as' the workpiece is linearly advanced through said abrasive stream.

15. In an abrading machine, a centrifugal abrasive propelling mechanism operative to project a stream of abrasive particles, a pair of spaced upper trackway members between which the abrasive stream from said propelling mechanism is projected, a pair of spaced lower trackway members, a pair of spacedspur trackway members extending to said lower trackway members, a'spur switch connecting said upper trackway members to said spurtrackway members, and a workpiece-supporting carriage supported by and movable over said trackway members.

16. In an abrading machine, an upper trackway and a lower trackway, a spur trackway and a trackway switch connecting said upper and lower trackways, `a workpiece-supporting carriage movable over said trackways, driven means connected to said carriage operative to. advance said carriage over said lower trackway, spur trackway, trackway switch and upper trackway,

17. In an abrading machine, a pair of spaced 70 trackways, a spur trackway and a trackway switch connecting said spaced trackways, a workpiece-supporting carriage movable over said trackways, meansassociated with said carriage operative to advance said carriage from one of 15 said spaced trackways to the other of said spaced trackways through the medium of said spurv trackway and trackway switch, and a centrifugal abrasive propelling mechanism positioned adjacent one of said spaced trackways operative to project a stream of abrasive particles against a workpiece supported on said carriage as said carriage is advanced over said adjacent trackway.

18. In an abrading machine, a circuitous trackway, a workpiece-supporting carriage movable over said trackway, a continuous flexible driven element operably connected to said carriage, means for driving said exible element to advance said carriage along said circuitous trackway, centrifugal abrasive propelling mechanism operative to project a downwardly directed fanshaped stream of abrasive particles positioned adjacent a section of said trackway, and driven means operating independently of said elementdriving `means for rotating the workpiece supported on said carriage while passing through the abrasive stream when the carriage moves through the trackway section adjacent said vabrasive propelling mechanism.

jacent said abrasive propelling mechanism forl rotating said workpiece-supporting means and the workpiece while the workpiece is advanced on said supporting carriage through said stream.

20. In an abrading machine, avcontinuous circuitous trackway comprising a pair of spaced generally parallel extending tracks, an endless drive member, a workpiece-supporting carriage having rollers movable over said trackway, means connecting said carriage to said endless drive member, means for driving said endless member to advance said workpiece-supporting carriage over said circuitous trackway, and a centrifugal abrasive projecting mechanism operative to project alstream of abrasive particles, said mechanism being positioned adjacent a section of said trackway to project the abrasive stream against the workpiece supported ,on said carriage and between said tracks while said carriage is advanced along said section of the trackway.

21. In an abrading machine, a continuous4 circuitous trackway including spaced guide means,

an endless relatively ilexible member extendingy along each of said guide means, a workpiecesupporting carriage including a carriage frame, and rollers rotatably mounted on said carriage frame and movable along said guide means, means connecting said carriage to said spaced flexible members, means for driving said ilexible members in unison to advance said workpiece-supporting carriage over said circuitous trackway, and a centrifugal abrasive propelling mechanism, said mechanism being positioned adjacent said circuitous trackway to project an abrasive stream against the workpiece supported on said carriage while said carriage is advanced, along said circuitous trackway.

DAVID C. TURNBUIL. 

